This application relates to a refrigerant system, wherein the compressor is a two-stage compressor, and wherein an intercooler is provided between the two compression stages. The intercooler is placed in the air stream moving over an indoor heat exchanger, and preferably downstream of an indoor heat exchanger, in relation to the airflow, such that an intercooler heat exchanger also provides a reheat function.
Refrigerant systems are known and utilized to condition a secondary fluid, such as air to be delivered into a climate controlled environment. Typically, a compressor compresses a refrigerant and delivers that refrigerant to an outdoor heat exchanger, known as a condenser for subcritical applications and as a gas cooler for transcritical applications. From the outdoor heat exchanger, the refrigerant passes through an expansion device, and then to an indoor heat exchanger, known as an evaporator.
To obtain additional capacity, enhance system efficiency and achieve higher compression ratios, it is often the case that a two-stage compressor is provided in a refrigerant system. With a two-stage compressor, two separate compressor members or two separate compressor units are disposed in series in a refrigerant system. Specifically, for instance, in the case of a reciprocating compressor, two separate compression members may be represented by different banks of cylinders connected in series. Refrigerant compressed by a lower stage to an intermediate pressure is delivered from a discharge outlet of this lower stage to a suction inlet of a higher stage. If the compression ratio for the compressor system is high (which is typically the case for two-stage compression systems) and/or refrigerant suction temperature is high (which is often the case for a refrigerant system equipped with liquid-suction heat exchanger), then refrigerant discharge temperature can also become extremely high, and in many cases, may exceed the limit defined by safety or reliability considerations. Thus, it is known in the art to provide an intercooler heat exchanger (or a so-called intercooler) between the two compression stages to extend the operational envelope and/or improve system reliability. In the intercooler, refrigerant flowing between the two compression stages is typically cooled by a secondary fluid. Typically, additional components and circuitry are required to provide cooling in the intercooler. As an example, a fan or pump is supplied to move a secondary cooling fluid from a cold temperature source to cool the refrigerant in the intercooler. This increases the cost of providing the intercooler function.
Another optional refrigerant system feature is a reheat circuit. In a reheat circuit, a refrigerant is passed through a heat exchanger located downstream in the path of air having passed over an evaporator. A control for the refrigerant system may then control the evaporator such that it will initially cool the air below a temperature that is desired by an occupant of the environment to be conditioned. This allows the removal of extra moisture amount from the air. The air then passes downstream over the reheat heat exchanger, and is warmed back to the desired temperature. The reheat circuit provides the ability to remove additional moisture from the air stream, when dehumidification is desired and no or little cooling is required. Typically, provision of a reheat circuit does require an additional heat exchanger, however, it does not require an additional air-moving device as it relies upon the air-moving device that is already provided to move air over the evaporator.
Recently, new generation refrigerants, such as natural refrigerants, are being utilized in refrigerant systems. One very promising refrigerant is carbon dioxide (also known as CO2 or R744). Particularly with CO2 refrigerant systems, the intercooler becomes even more important as these systems tend to operate at high discharge temperatures due to high operating pressures, frequent use of liquid-suction heat exchanger, and, in general, by the transcritical nature of the CO2 cycle, as well as a high value of the polytropic compression exponent for the CO2 refrigerant. However, the additional cost of the circuitry and components associated with the intercooler makes the provision of an intercooler less desirable.
Thus, it is desirable to provide an intercooler for a multi-stage compressor refrigerant system, and particularly for a CO2 refrigerant system, as well as a reheat function, that essentially does not require any additional circuitry or components beyond the intercooler itself.